Cushing — Geology of Clintox County. 



555 



these are thin-bedded, rather shaly hands, with an abundant brachiopod 

 fauna. Just beyond the three corners, a little over a mile north of Pitts- 

 burgh, is an east and west fault, bringing up again the upper beds of the 

 lower division on the north side. This is followed at once by the Maclwrea 

 beds again, and thence northward the entire Marl urea division and a large 

 part of the Tipper Chazy appear within the space of a mile, the latter w ell 

 exposed and abundantly fossiliferous. The final exposures are less than half 

 a mile from the Beekmantown line, and are succeeded, in the direction of dip. 

 just across that line by massive dolomites of Calciferous age. If the section of 

 the Chazy here be combined with the Bluff Point section, a nearly complete 

 exhibit of that formation is obtained. 



Trenton limestone. The best exposures of the Trenton to be found in 

 the county are in this township, but the base, the Black River limestone, is 

 nowhere exposed. Along the lake shore, just south of Bluff Point, and 

 extending for a third of a mile, are beds of Trenton age. They are separated 

 from the Bluff Point Chazy by an east and west fault, with a throw t<> the 

 north of about 200 feet. A small stream occupies the fault line. The section 

 exposes some 100 feet of the Trenton. At the south end the dip is steep, the 

 beds being tipped up along the fault. The rock is, for the most part, a black 

 slaty limestone with lighter colored limestone bands toward the base, which 

 contain the brachiopod fauna characterizing the lower 100 feet of the 

 Trenton in Chazy township). The upper two-thirds of the section is quite 

 barren of fossils, occasional trilobite fragments occurring. Similar beds 

 are found in the same position on Crab island, which lies one mile t<> 

 the eastward. The section there has already been briefly described. The 

 island is structurally a low - anticlinal fold, pitching to the north about five 

 degrees. The upper 100 feet of rock exposed there, carrying a lamellibranch 

 fauna, is shown nowhere else in the county. 



On Cumberland head, and thence northward into Beekmantown, are the 

 slaty exposures already described. They are younger than any of the Crab 

 island Trenton, and separated from that by an unknown vertical interval. 

 Just south of the breakwater at Plattsburgh, similar slates are exposed on the 

 shore, in which no fossils have been found, but in which thorough search 

 should be made, as they may be found to partially fill this gap. Litho- 

 logically they resemble the Cumberland head series much more than they 

 do the ordinary Trenton. 



Faults in Series IV. The whole Palaeozoic series is greatly faulted. 

 Though much remains to be done in working out the faults, especially the 



